“You can join the army at 16 or drive but now you can’t have your tongue pierced. That’s stupid,” says Toni, who has a “snakebite” - two piercings on her lower lip that bring to mind a serpent’s fangs.

“I like the way piercings look and I’ve never had any problems with them,” she says. “We go to reputable places for our piercings that know what they are doing and we’re old enough to look after them.”

The discussion took place on the back seat of a bus carrying the teenagers home from college in Ebbw Vale, south Wales. Shauna, whose piercings include a striking jewel on the back of her neck, suggests the law could cause more problems that it solves.

It says there are concerns that because children continue to grow during their teenage years, an intimate piercing performed at a young age could result in complications as bodies develop.

Young people might also be less likely to have the experience or knowledge of how to clean or maintain an intimate piercing, leading to an increased risk of infection, it says. The government is also concerned that intimate piercing can put young people in a vulnerable position.

Under the law, which came into force on Thursday, it is illegal for practitioners to carry out or arrange piercings in 10 body areas including the tongue, breast, genitals and buttocks.

Jazmyn, 16, who lives in the south Wales village of Hengoed, is more sympathetic to the government than Toni, Shauna and Talia. She had her tongue pierced when she was 15. “It was a little painful but I don’t regret it,” she says.

Jazmyn, 16, thinks the law is a good idea. Photograph: Francesca Jones for the Guardian

Jazmyn has 10 piercings including one on her wrist. “But I think the law is a good idea. I don’t mind waiting a little longer. I think lots of young people don’t know how to look after piercings so well. It seems sensible to me,” she says.

The day after his 18th birthday Ethan, in school uniform, is at Abracadabra in Blackwood, one of the most popular tattoo and piercing studios in the south Wales valleys. He is booking his first tattoo – a bass guitar fret – but is happy to talk about his piercings.

“I had my ear lobe done when I was 12. My parents took me to have it done,” he says. Since then he has become more adventurous and has “scaffolding”, which connects two or more piercings in the ear, as well as a nose ring. Intimate piercings, however, do not appeal. “Kids don’t really know what they are doing and not all parents look after their piercings so I think the law is a reasonable idea,” he says.

Ethan, who had his first piercing aged 12. Photograph: Francesca Jones for the Guardian

Marie Fleet, a tattoo artist and piercer at Abracadabra, says that until now studios followed their own rules. They charge £20 for a nipple piercing, £35 for a tongue or what they discreetly call a “personal female” and £40 for a “personal male”.

“But even before the law we wouldn’t do nipples or down below for under-18s. We’ve had girls of 11 wanting some inappropriate piercings. We turn them away,” she says.

Chris Stephens, the boss of the Big Redz piercing team, which works across south Wales and further afield, says he believes elements of the new law – such as the ban on tongue piercing – are bizarre. “It’s odd that has been classed as intimate piercing,” he says. Stephens points out that there were other mouth piercings such as the “smiley”, a piece of jewellery fixed to the tissue connecting the gum to the lip, which were not covered by the law.

At Vicky’s piercing studio in Ebbw Vale, the owner, Vicky Chappell, shows off her framed notice setting out the new law. But she worries that the legislation may drive some intimate piercing underground. “If the kids want a piercing they’ll find a way to get it,” she said. “They’ll go to a dodgy place or have it done when they’re on holiday.”

One of her sons wanted an eyebrow piercing recently. She refused to do it herself, worried that it would leave scarring. “He just took off and had it done somewhere else,” she says. “That’s the thing with teenagers. If they get something into their heads they will find a way.”